Outdoor furniture presents many challenges and opportunities to furniture and textile designers. Designers are seeking to make outdoor furniture resemble indoor furniture to a larger degree. The latest outdoor furniture seeks to mimic not only the appearance, but also the comfort, hand, and function of indoor furniture. Designing fabric with these qualities that is suitable for use on outdoor furniture is often difficult. Unlike indoor fabrics, a fabric that is “suitable for outdoor use” is subject to much harsher conditions over an extended period of time. Moisture, UV radiation from the sun, and fluctuating temperatures, which range from the heat of summer to the cold of winter, all heavily degrade the materials most commonly found in indoor fabrics, such as polyester. This degradation traditionally can be defined by physical property changes, such as tenacity reduction and/or elongation reduction of a yarn or fabric. A change in color or surface gloss of the material is also an indicator of degradation.
There are several accelerated test methods that can be used to measure a yarn or fabric's suitability to be used outdoors. A weatherometer using xenon arc lamps, or a QUV accelerated weathering tester using UV florescent lamps, are examples of machines capable of these accelerated methods. Test methods, such as SAE J2527 (version February 2004), combine the use of water spray with cycles of light and dark exposure to a prescribed xenon light source within the testing device. The xenon source is controlled at 0.55 Wm2 at 340 nm irradiance. However, the total spectral band ranges from 290-800 nm. A sample is “suitable for outdoor use” based on color and gloss loss if, after total exposure of at least 1500 KJs in method SAE J2527, the sample maintains at least a grade 3 on the Grey Scale colorfastness test. As is known in the art, Grey Scale is a well-recognized visual test of colorfastness providing grades from 1 to 5, where grade 5 represents minimal or no change and grade 1 represents severe change in color. This evaluation can be completed by a trained technician or an instrument such as a spectrophotometer.
One style of outdoor furniture ripe for improvement is sling furniture. Generally recognized in the art, sling furniture is characterized by a fabric panel or “sling” supported and held in a taut manner upon a frame. An example of a sling chair 10 is shown in FIG. 1. The sling chair 10 has a frame 12 and one or more sling panels 14. The sling panel 14 may be held along two or more edges, depending upon the design of the frame 12. Sling type construction is gaining popularity on indoor furniture, such as office chairs. The fabric used on these indoor office chairs provides significant comfort by using fabric that is able to stretch and recover. Common materials in these fabrics include bare co-polyester thermoplastic elastomers, such as Hytrel® from Dupont™. However, use of bare co-polyester thermoplastic elastomers means that these fabrics would be expected to degrade and/or fade rapidly, and therefore are generally known as unsuitable for outdoor use. Carbon black pigment can be added to the thermoplastic elastomer in order to support performance when used outdoors, but the color offering for decorative products becomes severely limited if only black is available. FIGS. 2a and 2b show the effects on elongation loss percentage and break strength of a bare Hytrel® yarn that includes black pigment and a UV package. This sample was subject to UV in accordance with AATCC 169 (2003). After exposure of 1320 KJs, the bare sample had lost more than half of its ability to elongate. UV exposure resulted in a reduction of more than 30% in break strength as well. Like SAE J2527, the AATCC 169 method can be used to evaluate a product's potential for outdoor use. This method specifies conditions at 77° C. with a continuous light source ranging from 290-800 nm. This method has been found to be detrimental to many polymers.
Known outdoor sling fabrics incorporate high tenacity high modulus polyester yarns that are coated with PVC. Use of these PVC coated polyester yarns generally have the necessary stability and durability for use on outdoor furniture. Known outdoor sling fabrics, however, may provide less comfort compared to recent indoor sling fabrics, because the outdoor fabrics are less capable of stretch and recovery. Therefore, there is a need for fabrics that are suitable for use in outdoor sling furniture that provide the stretch and recovery characteristics known to support a comfortable sit for the user.